It depends how much time you have. For castles you can go to Windsor Castle or Hampton Court - both which are just outside of London. Or, of course the Tower of London, in the heart of the city. For nature you could enjoy our many parks in the city - or go up to Hampstead Heath with views over-looking the city (find the place where Guy Fawkes hoped to watch Parliament burn) or maybe visit Kew Gardens where the Royal Botanic Gardens can be found together with lots of wonderful exhibitions. That should all keep you fairly busy :))) Better here I think!

If time is short, just walking in London will revel thousands of interesting places. If you stay in London itself, most places are within a few minutes walk of a Tube station. Walk along the South bank of the Thames between Tower Bridge and Westminster Bridge Visit Tate Modern Visit the 'Brain's exhibition at the Wellcome Trust http://www.wellcomecollection.org/whats-on/exhibitions/brains.aspx Go to the Covent Garden for interesting shops and street life Be a tourist - go and see Big Ben, but then ride the Underground from Westminster Station Take a riverboat tour to Greenwich Avoid Madame Toussaud's - it's just a waxworks! etc etc etc etc

Of course you want to visit Buckingham Palace and see the changing of the guard. The National Gallery is wonderful also. Westminster Abbey is also a wonderful site to visit. The British museum is also a good place to go. Stonehenge is a day trip away from London but easy to get to. Windsor Castle is awesome. Don't forget that London has many wonderful theatre's also. Have a wonderful trip.

It depends how much time you have. For castles you can go to Windsor Castle or Hampton Court - both which are just outside of London. Or, of course the Tower of London, in the heart of the city. For nature you could enjoy our many parks in the city - or go up to Hampstead Heath with views over-looking the city (find the place where Guy Fawkes hoped to watch Parliament burn) or maybe visit Kew Gardens where the Royal Botanic Gardens can be found together with lots of wonderful exhibitions. That should all keep you fairly busy :)))

Ralph, I like Nature and ancient castles. Recommend you anything?